When producing hydrocarbons or other fluids from an underground formation, a string of production tubing is typically run into the reservoir to provide a conduit to the surface for the produced fluids. Depending on the type of artificial lift applied to the formation, a rod string will often be located within the production string. Some types of servicing include running coiled tubing into the production string, in some cases to the bottom of the well.
A progressive cavity pump (a “PCP”) is an example of a commonly-used artificial lift apparatus for producing hydrocarbons or other fluids from underground reservoirs. A PCP includes a helical rotor/stator pair with corresponding surfaces to advance a cavity between the rotor and the stator uphole when the rotor is rotated relative to the stator. The stator is located at the end of the production tubing and the rotor is located within the stator at the downhole end of the rod string. Where a PCP is used to produce fluids from reservoirs including a significant amount of debris, the PCP may become blocked by the debris. When this occurs, the PCP must be serviced, which necessarily interrupts production. Greater complexity in servicing the PCP will typically lead to longer processes for servicing the PCP and correspondingly greater delay costs.
In some heavy oil reservoirs, a PCP may become clogged with sand, or “sanded off” during production. Standard practice is to apply a process including pulling the entire rod string including the PCP rotor, running coiled tubing into the production string to the stator, cleaning the stator, pulling the coiled tubing, running the rod string back into the production string to secure the rotor within the stator, and resuming production. This process often results in significant interruption of production and associated costs.
It is, therefore, desirable to provide an approach to cleaning a PCP or other downhole servicing which results in lowered costs associated with previous approaches.